CA 125 is a tumor-associated antigen expressed on greater than 80% of all non-mucinous ovarian epithelial tumors of serous, endometrioid, clear cell and undifferentiated histologies. Bast, R. C., Jr. et. al., J. Clin. Invest. 68:1331-1337, 1981; Kabawat, S. E. et. al., Am. J. Clin. Pathol., 79:98-104, 1983. The murine monoclonal antibody OC125 which reacts with CA 125 was generated by use of an established human serous cystadenocarcinoma cell line, OVCA 433. Bast, R. C., Jr. et. al., supra. Quantitation of this determinant in serum of patients with ovarian cancer has been made possible by the development of an immunoradiometric assay with OC125. Klug, T. L. et. al., Cancer Res., 44:1048-1053, 1984. The CA 125 antigenic determinant has also been reported to be found in human milk (Hanisch, F. G. et. al., Eur. J. Biochem., 149:323-330, 1985.), in normal cervical mucous (de Bruijn, H. W. A. et. al., Am. J. Obstet. Gynecol., in press) and in the central airway and normal lung tissue (Nouwen, E. J. et. al., Cancer Res., 43:866-876, 1986). In addition, CA 125 activity appears to exist in human seminal plasma.
The CA 125 determinant has been reported to be associated with a mucin-like high molecular weight glycoprotein complex. See e.g., Hanisch, F. G. et. al., Eur. J. Biochem., 149:323-330, 1985; Niloff, J. M. et. al., Am. J. Obstet. Gynecol., 151:981-986, 1986; Bast, R. C. et. al., Ovarian Cancer, pp. 23-35, Boston, Mass.: Martinus Nihofi, 1985; Masuho, Y. et. al., Cancer Res., 44:2813-2819, 1984; and Bast, R. C., Jr. et. al., Cancer Bull, 37:80-81, 1985. However, the lack of a procedure for isolation of CA125 antigen has impaired analysis of its chemical composition.